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  • Question regarding a sub panel tap

    Ok so first I'd like to say my main breaker/service disconnect is on a pole 100ft away from my house. 200amps.

    I had installed a 125 amp subpanel next to my 200 amp main distribution panel in preparation for my pv system. Using a 125 amp breaker providing power to the sub located inside of the main. After more research and a thread on this forum I'm realizing that the power from my pv system would ultimately land on the bus bars of the main which would violate the 120% rules.

    Does anyone see a problem if I were to remove the 125 amp breaker from the main panel, extend those wires to do a tap b4 the main 200amp breaker inside of my main panel to feed the subpanel. I would then need to install the 125 amp breaker in the backfeed slot of my subpanel, remove the load wires from the lugs inside of said panel, and connect them to the 125amp breaker providing over current protection for the feeder wires. In my peanut sized mind this would bypass my main so the 120 rule would only apply to the subpanel. I need 2x 40amp double pole breakers but I would opt for the 3rd option which tosses out the 120% rule and I'd be required to put a safety sticker on the subpanel stating that the combined ampacity of the breakers (excluding the supply) can't exceed the ampacity of the busbar.

    Thoughts opinions?

    I had considered doing 2 taps and adding 2x fused disconnects but this would be consideredably more work and I don't see how this method would protect the feeder circuit any differently than the tap to 125 amp breaker. Also I'm fairly confident in the legality of using the 3rd option.

    Basically this circuit is already wired up so were not talking about hypotheticals, I already have safety safety switches installed ect. I'm thinking I could possibly use like a fusible air conditioning disconnect in between the tap and the safety switches if I absolutely had to abandon the subpanel all together. It just stinks bc I got this subpanel inspected already and idk if my inspector would notice if I messed with it. Probably not but he might.

    I installed this subpanel over last winter and it never even occurred to me that It still wouldnt help me in the current configuration. I guess I shouldn't be surprised, I've basically done everything in this setup twice already, some things 3x...
    Last edited by Markyrocks69; 07-19-2019, 12:38 PM.

  • #2
    This is the way it is now....
    Attached Files

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    • #3
      This is the changes I'm proposing.

      I'd also like to add that this system isn't currently in operation, just to set everyone's mind at ease. I want to make 1000% sure that it's right b4 I get my final inspection.
      if you want a good laugh, I actually submitted a line drawing that shows the configuration as it is now, the subpanel ect with everything. The power company approved it.... so clearly they're depending on the inspectors to know what they're doing bc clearly they don't know or just don't care.
      Attached Files
      Last edited by Markyrocks69; 07-19-2019, 02:22 PM.

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      • #4
        You need to consult the local experts in your area. What my inspector might approve, yours won't. Same with power company agreements. Some areas don't allow line taps, some do.
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

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        • #5
          Originally posted by Mike90250 View Post
          You need to consult the local experts in your area. What my inspector might approve, yours won't. Same with power company agreements. Some areas don't allow line taps, some do.
          So after beating my half brothers ear for 3 days (hes supposedly been an electrician for 15-20 years) his final answer was that I need to replace my whole system but that the tap was legal if I followed the rules associated with said tap..... but me knowing that hes basically full of it.

          I gathered all my ducks in a row and called the electrical inspector. Apparently hes never even heard of a insulation piercing connector. Long story short hes fine with a line tap in the panel to feed a subpanel. It just cant be a splice. Its within 10 feet so theres really no special rules as long as the wire is rated at least 1/10th the amp rating of the service and/or sized to the amp rating of the equipment its supplying, whichever is bigger and that the ocpd is sized to the equipment that is being supplied. All pretty straightforward stuff.

          Again this would take my original msp out of the equation so I can in fact use the 3rd option that throws out the 120% rule. It's sad bc I had to explain what that was and why it was important. Smh. I could have just kept my mouth shut but I don't want my house to burn down.

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          • #6
            I'm not going to approve or disapprove of what you are doing as I'm not there to see or do it in person. This is what inspectors are for. But I will say that very few main service panels are "listed" for line side taps - that is, approved by the manufacturer and tested by UL and therefore not strictly what a building inspector will allow.
            BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installed

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            • #7
              Originally posted by solarix View Post
              I'm not going to approve or disapprove of what you are doing as I'm not there to see or do it in person. This is what inspectors are for. But I will say that very few main service panels are "listed" for line side taps - that is, approved by the manufacturer and tested by UL and therefore not strictly what a building inspector will allow.
              You are exactly 100% correct. The inspector sounded like he was more concerned that the connector I was planning on using was ul listed (which it is) and that there wasn't a splice in the panel than anything else. He didn't mention the box itself. You are correct about the box might not ul listed for that exact procedure. My inspector said that he would go along with anything that was reasonable. Those were his exact words. In my mind a metal box is a metal box, as long as the fitting is insulated and everything fits inside it seems pretty reasonable to do the operation. The only other option is to install a trough and do what I need to do inside of there. But that just seems like a waste of time bc a metal box is a metal box. Trust me I want everything to be safe.

              What I'm talking about is no different than this

              https://youtu.be/HGZM3rsfMcA

              Except my wires will be 2/0 and running directly to a subpanel with a 125 amp backfed breaker.

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              • #8
                Ok so just a quick update. Yesterday I was able to do my first test on my new inverters. There was a couple of tense moments but all seems to be working as intended. I did the test b4 I attempted to fix the way that the subpanel was connected. So last night I started messing with it. My first attempt didn't work for various reasons. So I initiated the nuclear option and ripped it completely apart. The original design of the conduit was just a disaster so I fixed all that.

                Here's a picture of the tap and the subpanel after it's all done. Its connected everything is working as intended.

                I'd also like to add that the taps are fully insulated even the bolt is isolated from current.

                O and don't mind the black spot behind the one main lug. That happened years ago when my stepfather was in there messing around. I think he was trying to electrocute himself and almost succeeded.
                Attached Files
                Last edited by Markyrocks69; 07-28-2019, 06:34 PM.

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